1. Field of the Invention
The invention relates to a device for transmitting or decoupling mechanical vibrations, comprising a first component and a second component, which are connected to each other by a coupling element having a variably adjustable stiffness in at least one direction of action, and along which at least one component is supported in a vibrating manner.
2. Description of the Prior Art
If two components are connected to one another via a mechanical coupling element, for example via a spring which can be deflected bidirectionally in a spatial direction, then in the event of a vibrational excitation of a component, a vibration transmission to the other component results from the coupling element. The vibration transmission between both components can be influenced by adjusting the stiffness of the coupling element. In the case of a low stiffness of the coupling element, the vibration transmission can be reduced.
If it is necessary for example to support a machine arrangement on a machine foundation with as little vibration as possible, then a coupling element is used which has a fixed predetermined stiffness or is inherent elasticity. However, if the machine assumes different vibration states as a function of the operating state, it may occur that the machine is operated at the natural frequency of the system composed of the coupling element and the machine. Pronounced vibration amplitudes occur in this resonant operating state, which may lead to increased noise and also increased mechanical loading of the system as a whole. Usually, machine operation and the stiffness of the coupling elements are adapted to one and another to prevent resonance or to pass through resonance in a short period when starting up the machine.
The indicated possibility for influencing the vibration transmission between two components by a coupling element can also be used, in addition to the above-mentioned low-vibration supporting of two components relative to one another, for eliminating the targeted vibration or reducing a vibrating component.
In this case, in the manner known per se, a so-called vibration absorber is connected to the vibrating component. To this end, a mass, called an absorber mass, is connected via a coupling element to the vibrating component. The resonant frequency or tuning frequency or absorbing frequency of the vibration absorber can be set by the absorber mass and also by the stiffness of the coupling element. As a result the vibrations of the component to be vibration damped are compensated in a narrow frequency band around the tuning frequency of the vibration absorber. In the case of alternating vibration states within the component to be vibration damped, it is furthermore advantageous to adapt the tuning frequency of the vibration absorber to the instantaneous excitation frequency, in order in this manner to variably construct the effective range of operation of the vibration absorber.
A range of differently constructed coupling elements is known for both of the previously mentioned use cases for a targeted influencing of the vibration transmission between two components. By using coupling elements it is possible to variably adapt a vibration reduction or complete vibration decoupling between two components in spite of changing vibration states by influencing the stiffness or elasticity.
As an example for a device with a low-vibration support of a component coupled to a foundation with a variably adjustable spring stiffness between component and foundation, a support unit is suggested by an article by Bonello, Philip et al, “Vibration Control Using an Adaptive Tuned Vibration Absorber with a Variable Curvature Stiffness Element”, in: Smart Materials and Structures 14 (5), pp. 1055-1065, (2005), which clamps two separately arcuately constructed spring elements between an upper bearing and lower support surface with a changeable stiffness produced by changing the pre-bending of the respective spring elements with the aid of an adjustment unit.
A device for vibration decoupling is described in DE 10 2005 043 429 A1, which has a completely peripherally damped planar membrane within a housing structure, on which a rod-shaped load-bearing having a longitudinally extending rod which extends orthogonally from the planar membrane, which is connected to a vibrating component. In order to influence the planar elasticity of the membrane, at least one actuator having a converter material is applied to the same which has the capacity to influence the deformability of the planar membrane.
Approaches using variably tuneable stiffness characteristics are also known for realizing vibration absorbers. One known embodiment for a vibration absorber has a centrally supported spring beam central support attached to a component which is to be vibration damped. An absorbing mass is attached to mutually opposite exposed spring beam ends. The absorbing masses vibrate with maximum amplitudes relative to the central support when the absorbing frequency is reached. To influence the absorbing frequency, piezoelectric actuators are applied on both sides of the central support along the spring beam, which influence planar elasticity of the spring beam. An alternative option for influencing the absorbing frequency of a previously described structure for a vibration absorber is disclosed by WO 2008/131740 A1. In this case, the spacing of the absorber masses supported on both sides along the spring beam relative to the central support is changed via a mechanical actuator. As a result, the change in exposed beam lengths the absorbing frequency changes.